The Signals of Doomsday I: False Higgs vacuum decay signatures

Abstract

The measured standard model parameters indicate that we might live in a false Higgs vacuum, though with a very long lifetime. However, small black holes can serve as catalysers and significantly speed up the phase transition. In fact, bubbles of true vacuum might already exist in our universe. If the propagation of the bubble walls slows down due to interaction with the surrounding matter and plasma, these signals can reach us before the bubble wall hits us. Using the vacuum mismatch method, we calculate the spectrum of the Higgs particles produced by such a bubble until the terminal velocity is reached. In addition, we show that frictional dissipation at the terminal wall velocity generates a large population of thermally produced Higgs particles, which continues even after the mismatch channel shuts off. Since the Higgs is neutral, a good part of the final decay products (after hadronization, annihilation and decay of unstable particles) will be photons and neutrinos, which will then act as a long-range signature. For the conservative set of parameters used here, the thermal channel produces a macroscopically large burst of high energy neutrinos and photons from Higgs decays, which could be detectable from sufficiently nearby bubbles with current or upcoming multi messenger facilities.

Figures (4)

• Figure 1: This figure shows the Higgs potential $V(\phi)$ in Eq. (\ref{['hp']}). The true vacuum is at $\phi\approx 3.6\times 10^{-2}M_p$. The parameters are chosen to be within the standard model, i.e. $b= 10^{-4}$, $\lambda_* = -0.001$, $\phi_* = 0.5M_p$, and $\lambda_6 = 0.34$Burda:2015isa.
• Figure 2: The Higgs field distribution at the moment when a black hole triggers the false vacuum decay. The inner black hole mass is $1 M_p$. The radius of the true vacuum bubble at that moment is $2\times 10^4 M_p^{-1}$. The parameters are the same as in Fig. \ref{['potential']}.
• Figure 3: Number density of Higgs particles as a function of their momenta created due to the vacuum mismatch in the Higgs vacuum decay. The units are given in terms of the Planck mass $M_p$.
• Figure 4: Physically normalised thermal spectrum ${\rm d}N/{\rm d}k$ for the Higgs-like scalar with mass $\mu = 7.16\times10^{-4}M_p$ produced via frictional dissipation. Each curve corresponds to a different terminal-velocity deficit $\delta$, which determines both the shock temperature and the total thermal particle number $N_{\rm th}$. The peak of each distribution occurs at $k_{\rm peak}\simeq 2.8T$, as expected for a massive Bose–Einstein spectrum. The vertical normalisation of the curves reflects the physical particle yields shown in Table \ref{['tab:thermal-yields']}.